Hussar, you'd be best to continue to build your points on AC because in all likelihood, even if an announcement about merging accounts occurs in the next few weeks, it is likely to take many months to actually happen.

As well, if you are hoping to go to the UK during the peak summer travel period -- not to mention peak redemption period for these routes -- you had better book your flights now so AC is the obvious carrier you'll use since 2 Y-class tickets will cost most all your points. You may or may not be able to use them on CP flights, but these too are likely to be filling quickly.